More than a month before Halloween, the most sophisticated horror stories are already crawling out of the ground. You think you're safe over there in the primly maintained Literary Fiction section of the cemetery, peering across the rusty gate at Stephen King's "Under the Dome" (Nov. 10), Anne Rice's "Angel Time" (Oct. 27) and even a sequel to "Dracula" written by -- please, no! -- Bram Stoker's great-grandnephew (Oct. 13). But meanwhile your genteel old friends have already been hideously transformed: Sarah Waters leads this bone-chilling pack with a Jamesean ghost story called "The Little Stranger," which has a good shot at winning the Booker Prize next week. Dan Chaon's "Await Your Reply" pays homage to everybody from Peter Straub to H.P. Lovecraft, and Mary Shelly's "Frankenstein" has been re-stitched by such non-horror writers as Peter Ackroyd and Laurie Sheck. In short, there's nowhere to hide this year from frighteningly smart, scary novels.

The latest to join this infernal group comes from Audrey Niffenegger, author of the phenomenally popular "Time Traveler's Wife," which means her new one has a good chance of haunting the bestseller list, too. As naturally as she used elements of science fiction in the past, she borrows the tropes of Victorian Gothic here for a story that seems, at first, more interested in whimsy than terror. "Her Fearful Symmetry" doesn't reveal its spectral elements for more than 60 pages, and when the first ghost does make an appearance, "gaining opacity gradually," the scene is strangely poignant and witty, like a visitation from Noël Coward's "Blithe Spirit." But Niffenegger manages to breathe life into these dead cliches, noting at one point that the soul leaves the body "slippery like an avocado stone popping out."

Millions of readers who enjoyed "The Time Traveler's Wife," or endured the recent movie version, will find a similar theme in "Her Fearful Symmetry": romance that transgresses all natural barriers. But this new novel also recalls the odd illustrated book that Niffenegger published in 2006, "The Three Incestuous Sisters." A visual artist and printmaker, she spent 14 years working on the intaglio pictures for that tale of sibling rivalry, and "Her Fearful Symmetry" suggests that she's still preoccupied by this unsettling subject.

As the story opens, two college dropouts, identical twins Julia and Valentina Poole, have inherited an apartment in London and several million pounds from an aunt they never met, their mother's identical twin, Elspeth. With nothing else to do and no particular interests, the twins accept this generous bequest, leave their parents behind in Chicago and move into their late aunt's flat. Below them lives Elspeth's bereaved lover, a much younger man named Robert, who's writing a history of the cemetery next door. And above them lives Martin, an agoraphobic man with obsessive-compulsive disorder who writes esoteric crossword puzzles for several British newspapers.

"Her Fearful Symmetry" is rather thinly plotted and at least 100 dilatory pages too long. One chapter begins with the damning confession, "Days went by and nothing much happened." But Niffenegger creates such marvelous scenes of muted sadness and smothered affection that you don't entirely mind that the parts are better than the whole. Her portrayal of the lonely crossword writer, for instance, is funny and sad, even if never particularly integral to the story line. Surrounded by barrels of bleach, winding through his labyrinth of boxes while counting backward from 1,000 in Roman numerals, poor Martin is trapped in a loop of anxieties. He spends his days pining for a woman who loves him but can no longer endure his compulsive routines.

Meanwhile, Robert, the young historian who lives beneath the twins, fleshes out the story's Gothic trappings in all their luxurious agony. The subject of his ever-growing dissertation is London's Highgate Cemetery, where he volunteers as a guide, offering historical commentary to tourists and nursing his raw grief for Elspeth. Niffenegger is clearly in love with this beautiful, funereal place, too; she worked as a guide there herself, and at the end of the novel she includes a plea for donations that's hard to resist. For Robert, Highgate is a prism "through which he could view Victorian society at its most sensationally, splendidly, irrationally excessive . . . a theatre of mourning, a stage set of eternal repose." In other words, it's the perfect place to tempt a rational young man into macabre speculation about contacting his dead lover. But what starts like Patrick Swayze's erotic pottery scene in "Ghost" eventually slips off center to something closer to Alfred Hitchcock's "Vertigo."

Niffenegger slowly draws out the relationship between the indolent young twins in a strange dance that's alternately charming and sinister. Julia and Valentina, it turns out, aren't exactly identical -- they're "mirror-image twins"; all Valentina's internal organs are on the other side of her body. "They were essentially one creature," Niffenegger writes, "whole but containing contradictions." The fey one, Valentina, wants to study fashion design, while her more aggressive sister just wants to keep her safe. Their sisterly devotion sounds sweet until it seems suffocating, with a touch of incestuous frisson that would leave Edgar Allan Poe queasy.

Tensions between Valentina and her controlling twin eventually push the plot to a bizarre crisis involving body-snatching and soul-swapping. It's a disorienting shift into the dark logic of fairy tales. But keep the children away and dust off the Ouija board; you're about to make contact with something deliciously creepy.